Consumption is a fusion of the Planescape, Ravenloft, and Underdark campaign settings. It takes place in a planar anomaly: an immense set of caverns that cut through material excreted by the Demiplane of Dread. The game is evil-focused and high-powered, featuring Gestalt rules and a huge number of allowed sources. Characters are fairly high in level, and the game is designed to go epic at a certain point.
Player characters are either native to the Underdark environment of the setting, or are drawn in by planar accident. This is a frequent occurrence: when the Dark Powers desire to draw a being into Ravenloft, the effort is rarely completely accurate and causes great stress to the planar structure. Frequently beings fall through the cracks, to wind up in Consumption. This is one of the most advantageous features of the setting: player characters can plausibly be generated using virtually any combination of races, classes, templates, and abilities the DM wishes to allow.
A second advantage of Consumption is the sealed nature of the setting. Existing on the far side of Ravenloft, it is well cut off from the rest of existence. Attempting to cross the Demiplane of Dread via Astral travel, Ethereal travel, or any other means generally draws the attention of the Dark Powers. They most often result in the would-be traveler becoming the Dark Lord of an Island of Terror, or cast into the Nightmare Lands. Telepathic messages, divinations, and other information-exchanging powers also function at the whim of the Dark Powers, and are subsequently unreliable.
Consumption offers players great freedom and power, while allowing the GM to maintain control and focus on the setting.